This application claims the benefit of a Japanese Patent Application No. 2000-363900 filed Nov. 29, 2000, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to disk units, and more particularly to a disk unit which loads a head with respect to a disk from a holding mechanism when making an access to the disk, and unloads the head from the disk to the holding mechanism when making no access to the disk.
There are demands to increase the storage capacity of information storage apparatuses such as magnetic disk units. In order to increase the storage capacity, it is necessary to increase a recording region on the disk.
In the magnetic disk unit, the disk rotates at a predetermined speed. The head is arranged to confront the disk, and is held in a state where the head slightly floats from the disk due to the rotation of the disk. The head can record information on and/or reproduce information from the disk in this floating state, without making direct contact with the disk. Accordingly, the disk is prevented from being damaged by the head.
The head floats from the disk when the disk rotates at the predetermined speed. When the rotational speed of the disk is reduced or the disk stops rotating, the head may make direct contact with the disk. For this reason, a holding mechanism which is often referred to as a ramp mechanism is provided to hold the head to a receded position where the head will not make direct contact with the disk.
2. Description of the Related Art
FIGS. 1A, 1B and 2 are diagrams for explaining an example of a conventional disk unit. FIG. 1B is a plan view of the conventional disk unit, and FIG. 1A is a cross sectional view of the conventional disk unit taken along a one-dot chain line in FIG. 1B. FIG. 2 is a system block diagram showing the conventional disk unit.
As shown in FIGS. 1A and 1B, a disk unit (HDD: hard disk drive) 10 generally includes a disk enclosure (DE) 11 and a printed circuit assembly (PCA) 12. The disk enclosure 11 includes a disk 111, a spindle motor 112, a voice coil motor (VCM) 113, an arm 114, a head 115, and a ramp mechanism (holding mechanism) 116.
The disk 111 is rotatable in a direction A by the spindle motor 112. In addition, the arm 114 is pivotable in a direction B by the voice coil motor 113. The head 115 is fixed at a tip end of the arm 114. By pivoting the arm 114 in the direction B by the voice coil motor 113, the head 115 moves in a radial direction of the disk 111, so that the head 115 can scan a desired track on the disk 111. The ramp mechanism 116 is arranged on an outer periphery of the disk 111. The ramp mechanism 116 engages the tip end of the arm 114, and separates the head 115 from the disk 111 and to hold the head 115 in this separated position.
As shown in FIG. 2, the head 115 reproduces a signal from the disk 111, and supplies the reproduced signal to a head IC 117 which amplifies the reproduced signal before supplying the reproduced signal to the printed circuit assembly 12. A recording signal from the printed circuit assembly 12 is supplied to the head via the head IC 117, so as to record the recording signal on the disk 111.
The printed circuit assembly 12 includes a hard disk controller (HDC) 121, a RAM 122, a ROM 123, a MPU 124, a read channel (RDC) 125, a servo controller (SVC) 126, and drivers 127 and 128.
The MPU 124 executes a program stored in the ROM 123, and controls the voice coil motor 113 via the servo controller 126, so as to carry out a ramp load operation of a ramp unload operation. The ramp load operation loads the head 115 on the disk 111 from the ramp mechanism 116, and the ramp unload operation unloads the head from the disk 111 to the ramp mechanism 116.
In the conventional disk unit 10, the ramp load operation is carried out immediately when a ramp load command from the hard disk controller 121 is recognized, and the ramp unload operation is carried out immediately when a ramp unload command from the hard disk controller 121 is recognized. Hence, a position where the head 115 is loaded on the disk 111 from the ramp mechanism 116, and a position where the head 115 is unloaded from the disk 111 to the ramp mechanism 116 are not specified.
For this reason, in order to prevent an error caused by damage to the disk 111 by the head 115 during the ramp load operation and/or the ramp unload operation, a data recording prohibit region Ad is provided on the disk 111 as shown in FIG. 3. FIG. 3 is a diagram for explaining the data recording prohibit region Ad in which the data recording is prohibited. The data recording prohibit region Ad has a ring shape, as indicated by the hatching in FIG. 3. This data recording prohibit region Ad corresponds to the position where the head 115 is loaded by the ramp load operation and the position where the head 115 is unloaded by the ramp unload operation.
However, according to the conventional disk unit 10, an increase of the storage capacity is limited by the data recording prohibit region Ad which is provided on the disk 111 to prevent an error from being generated due to the damage to the disk 111 by the head 115 during the ramp load operation and/or the ramp unload operation. Since the data recording prohibit region Ad is provided in the ring shape in the outer peripheral region of the disk 111 and the data recording density is higher in the outer peripheral region of the disk 111, there is a problem in that the increase of the storage capacity is greatly limited by the data recording prohibit region Ad.